Conventionally, for example, Japanese Patent Laid-Open No. Hei5-223612 has disclosed a liquid gas remaining quantity managing device for calculating the remaining quantity in a liquid gas cylinder from the integrated flow quantity of gas. In this device, the flow quantity is always measured by a mass flow meter provided to a gas supply line. The measured flow quantity is added by an integrating meter, and the integrated quantity used is calculated, by which the remaining quantity of gas is managed.
Patent Document 1:
Japanese Patent Laid-Open No. Hei5-223612
Patent Document 2:
Japanese Patent Laid-Open No. Hei7-49254
Patent Document 3:
Japanese Patent Laid-Open No. 2001-272266